1. Field of the Invention
The present invention relates to a branch joint for a high-pressure fluid (e.g., a fluid under a high pressure over 1,000 Kgf/cm.sup.2) to be used in a cutter or a washer using high-pressure water, a hydraulic working machine, or a high-pressure hydraulic apparatus.
2. Description of the Prior Art
In one of this kind of branch pipe joint of the prior art, as shown in FIGS. 7 and 8, a joint body 11 having a conduit 11-1 therein on its axis is equipped with a boss 11-4 which has a branch hole 11-2 on the center line of the conduit 11-1. This branch hole 11-2 has a circumference communicating with the conduit 11-1 and opened to the outside to form a pressure receiving seat 11-3. A pressure seat 12-3, as formed on a joint head 12-2 of a branch pipe 12, is brought into abutting engagement with the pressure receiving face 11-3 of the joint body 11, so that the branch pipe 12 is connected to the joint body 11 by fastening a cap nut 13 on the boss 11-4 through a fastening washer 14 screwed on the leading end of the branch pipe 12. The joint body 11 is provided at each of its two ends with a pressure receiving face 11-5 which is formed in the opening of the conduit 11-1, as in the joint structure of the branch pipe. This pressure receiving face 11-5 is formed on the circumference of the conduit 11-1 and opened to the outside. A pressure seat 15-3, as formed on the joint head 15-2 of a main pipe 15, is brought into abutting engagement with the pressure receiving face 11-5 of the joint body 11, so that the main pipe 15 is connected to the joint body 11 by fastening a cap nut 16 on the joint body 11 through a fastening washer 17 screwed on the leading end of the main pipe 15. Reference numeral 12-1 designates a conduit of the branch pipe, and numeral 15-1 designates the conduit of the main pipe 15.
In the high-pressure fluid branch pipe joint of the prior art in which the branch hole 11-2 having a circular section is formed in the joint body 11 in alignment with the conduit 11-1 of the joint body 11, however, the highest stress is established at the open end P of the conduit 12-1 of the branch pipe 12 at the joint body conduit 11-1 when the internal pressure acts upon the joint body 11, so that a crack is liable to start from the open end P thereby to invite a leakage of the fluid.